It is often necessary or desirable for a person to exercise a particular muscle or group of muscles, such as to recover from surgery or injury, to increase strength, stamina and endurance, and to maintain an active and healthy lifestyle, as well for aesthetic purposes. Various machines have been developed to exercise different muscles and muscle groups by forcing the muscles to contract and extend under a load, such as by moving a free weight against the force of gravity or by moving an object whose movement is resisted by resistance force, such as a, spring or a weight attached to a cable and pulley system.
One exercise that has been developed to exercise the leg muscles is known as the leg press. A leg press involves a pushing motion wherein a person pushes with his/her feet and legs to extend the legs from a hip and knee flexed starting position to a hip and knee extended finishing position, thereby contracting the muscles in the legs and lower torso, namely the quadriceps, gluteal, and calf muscles, as well as any ancillary muscles involved in such a motion.
A typical leg press machine includes a footplate and a seat. A user sits in the seat, generally facing opposite the footplate, applies force to the footplate in the leg press motion, which is typically a compound motion of the hip and knee pushing the footplate away from the user's torso. This force is countered by the force generated by the hip and knee applied through the torso against the seat, rendering the body relatively motionless with respect to a fixed frame such as the ground. As the legs extend, either the footplate or the seat (or both) is moved, generally in a somewhat linear path, allowing the exercise motion to proceed. A resistance device is coupled to the moving elements to provide the necessary resistance.
Currently, leg press exercise machines having features similar to those disclosed in Jones, U.S. Pat. No. 5,106,080, and Simonson et al., U.S. Pat. No. 5,263,914, include an adjustable seat for accommodating users having different body sizes and leg lengths. The position of the seat relative to the footplate is adjusted prior to the commencement of exercise such that the user can exercise over a full range of motion. Alternatively, the footplate may be disposed at various initial positions with respect to a fixed seat.
In known leg press machines, the motion of the moving portion of the machine is generally fixed to one linear or rotational degree of freedom. Thus, when the leg press exercise is executed, the body or the machine move in a generally linear, straight translational motion or a single axis rotational motion. This results in an exercise which mostly stresses the quadricep muscle group in the leg, but does not fully engage various other muscle groups in the hips and lower torso, which are often integral to the motion of the lower body. Examples of such muscle groups are the hip extensor and lower back muscles.
It is desirable therefore, to provide an exercise machine for the legs, which also incorporate a means by which the hips and lower back muscles may be exercised to a higher intensity and with a greater range of motion, in addition to the muscles exercised by a traditional leg press.